Black lithium silicate glass ceramics

ABSTRACT

A black lithium silicate glass ceramic is provided. The glass ceramic includes lithium silicate as a primary crystal phase and at least one of petalite, β-quartz, β-spodumene, cristobalite, and lithium phosphate as a secondary crystal phase. The glass ceramic is characterized by the color coordinates: L*: 20.0 to 40.0, a*: −1.0 to 1.0, and b*: −5.0 to 2.0. The glass ceramic may be ion exchanged. Methods for producing the glass ceramic are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 62/592,715 filed on Nov. 30, 2017, the contents ofwhich are relied upon and incorporated herein by reference in theirentirety.

BACKGROUND Field

The present specification generally relates to glass ceramiccompositions. More specifically, the present specification is directedto black lithium silicate glass ceramics that may be formed intohousings for electronic devices.

Technical Background

Portable electronic devices, such as, smartphones, tablets, and wearabledevices (such as, for example, watches and fitness trackers) continue toget smaller and more complex. As such, materials that are conventionallyused on at least one external surface of such portable electronicdevices also continue to get more complex. For instance, as portableelectronic devices get smaller and thinner to meet consumer demand, thehousings used in these portable electronic devices also get smaller andthinner, resulting in higher performance requirements for the materialsused to form these components.

Accordingly, a need exists for materials that exhibit higherperformance, such as resistance to damage, and a pleasing appearance foruse in portable electronic devices.

SUMMARY

According to aspect (1), a glass ceramic is provided. The glass ceramiccomprises: at least one lithium silicate crystal phase as a primarycrystal phase; and at least one of petalite, β-quartz, β-spodumene,cristobalite, and lithium phosphate as a secondary crystal phase. Theglass ceramic is characterized by the following color coordinates: L*:20.0 to 40.0; a*: −1.0 to 1.0; and b*: −5.0 to 2.0.

According to aspect (2), the glass ceramic of aspect (1) is provided,wherein the primary crystal phase is a lithium metasilicate.

According to aspect (3), the glass ceramic of aspect (1) or (2) isprovided, wherein the primary crystal phase is lithium disilicate.

According to aspect (4), the glass ceramic of any of aspects (1) to (3)is provided, wherein the glass ceramic has a transmittance of less thanabout 1% in the visible light range.

According to aspect (5), the glass ceramic of any of aspects (1) to (4)is provided, wherein the glass ceramic has a ring-on-ring strength of atleast about 290 MPa.

According to aspect (6), the glass ceramic of any of aspects (1) to (5)is provided, wherein the glass ceramic has a fracture toughness of about0.9 MPa·m^(0.5) to about 2.0 MPa·m^(0.5).

According to aspect (7), the glass ceramic of any of aspects (1) to (6)is provided, wherein the glass ceramic has a fracture toughness of about1.0 MPa·m^(0.5) to about 1.5 MPa·m^(0.5).

According to aspect (8), the glass ceramic of any of aspects (1) to (7)is provided, further comprising: about 55.0 wt % to about 75.0 wt %SiO₂; about 2.0 wt % to about 20.0 wt % Al₂O₃; 0 wt % to about 5.0 wt %B₂O₃; about 5.0 wt % to about 15.0 wt % Li₂O; 0 wt % to about 5.0 wt %Na₂O; 0 wt % to about 4.0 wt % K₂O; 0 wt % to about 8.0 wt % MgO; 0 wt %to about 10.0 wt % ZnO; about 0.5 wt % to about 5.0 wt % TiO₂; about 1.0wt % to about 6.0 wt % P₂O₅; about 2.0 wt % to about 10.0 wt % ZrO₂; 0wt % to about 0.4 wt % CeO₂; about 0.05 wt % to about 0.5 wt % SnO+SnO₂;about 0.1 wt % to about 5.0 wt % FeO+Fe₂O₃; about 0.1 wt % to about 5.0wt % NiO; about 0.1 wt % to about 5.0 wt % Co₃O₄; 0 wt % to about 4.0 wt% MnO+MnO₂+Mn₂O₃; 0 wt % to about 2.0 wt % Cr₂O₃; 0 wt % to about 2.0 wt% CuO; and 0 wt % to about 2.0 wt % V₂O₅.

According to aspect (9), the glass ceramic of any of aspects (1) to (8)is provided, further comprising: about 65.0 wt % to about 75.0 wt %SiO₂; about 7.0 wt % to about 11.0 wt % Al₂O₃; about 6.0 wt % to about11.0 wt % Li₂O; about 2.0 wt % to about 4.0 wt % TiO₂; about 1.5 wt % toabout 2.5 wt % P₂O₅; about 2.0 wt % to about 4.0 wt % ZrO₂; about 1.0 wt% to about 4.0 wt % FeO+Fe₂O₃; about 0.5 wt % to about 1.5 wt % NiO; andabout 0.1 wt % to about 0.4 wt % Co₃O₄.

According to aspect (10), the glass ceramic of any of aspects (1) to (9)is provided, wherein the glass ceramic has a crystallinity of greaterthan about 50 wt %.

According to aspect (11), the glass ceramic of any of aspects (1) to(10) is provided, wherein the glass ceramic is ion exchanged andcomprises a compressive stress layer extending from a surface of theglass ceramic to a depth of compression.

According to aspect (12), the glass ceramic of aspect (11) is provided,wherein the glass ceramic has a compressive stress at the surface of atleast about 250 MPa.

According to aspect (13), the glass ceramic of aspect (11) or (12) isprovided, wherein the glass ceramic has a compressive stress at thesurface of about 250 MPa to about 650 MPa.

According to aspect (14), the glass ceramic of any of aspects (11) to(13) is provided, wherein the depth of compression is at least 0.05t,where t is a thickness of glass ceramic.

According to aspect (15), the glass ceramic of any of aspects (11) to(14) is provided, wherein the glass ceramic has a ring-on-ring strengthof at least about 900 MPa.

According to aspect (16), a consumer electronic product is provided. Theconsumer electronic product comprises: a housing comprising a frontsurface, a back surface and side surfaces; electrical components atleast partially within the housing, the electrical components comprisingat least a controller, a memory, and a display, the display at oradjacent the front surface of the housing; and a cover glass disposedover the display. At least a portion of the housing comprises the glassceramic of any of aspects (1) to (10).

According to aspect (17), a consumer electronic product is provided. Theconsumer electronic product comprises: a housing comprising a frontsurface, a back surface and side surfaces; electrical components atleast partially within the housing, the electrical components comprisingat least a controller, a memory, and a display, the display at oradjacent the front surface of the housing; and a cover glass disposedover the display. At least a portion of the housing comprises the glassceramic of any of aspects (11) to (15).

According to aspect (18), a method is provided. The method comprises:ceramming a precursor glass-based article to form a glass ceramic. Theglass ceramic comprises: at least one lithium silicate crystal phase asa primary crystal phase; and at least one of petalite, β-quartz,β-spodumene, cristobalite, and lithium phosphate as a minor crystalphase. The glass ceramic is characterized by the following colorcoordinates: L*: 20.0 to 40.0; a*: −1.0 to 1.0; and b*: −5.0 to 2.0.

According to aspect (19), the method of aspect (18) is provided, whereinthe ceramming occurs at a temperature of about 500° C. to about 900° C.

According to aspect (20), the method of aspect (18) or (19) is provided,wherein the ceramming occurs for a period of about 6 hours to about 16hours.

According to aspect (21), the method of any of aspects (18) to (20) isprovided, further comprising ion exchanging the glass ceramic.

According to aspect (22), the method of any of aspects (18) to (21) isprovided, wherein the precursor glass-based article comprises: about55.0 wt % to about 75.0 wt % SiO₂; about 2.0 wt % to about 20.0 wt %Al₂O₃; 0 wt % to about 5.0 wt % B₂O₃; about 5.0 wt % to about 15.0 wt %Li₂O; 0 wt % to about 5.0 wt % Na₂O; 0 wt % to about 4.0 wt % K₂O; 0 wt% to about 8.0 wt % MgO; 0 wt % to about 10.0 wt % ZnO; about 0.5 wt %to about 5.0 wt % TiO₂; about 1.0 wt % to about 6.0 wt % P₂O₅; about 2.0wt % to about 10.0 wt % ZrO₂; 0 wt % to about 0.4 wt % CeO₂; about 0.05wt % to about 0.5 wt % SnO+SnO₂; about 0.1 wt % to about 5.0 wt %FeO+Fe₂O₃; about 0.1 wt % to about 5.0 wt % NiO; about 0.1 wt % to about5.0 wt % Co₃O₄; 0 wt % to about 4.0 wt % MnO+MnO₂₊Mn₂O₃; 0 wt % to about2.0 wt % Cr₂O₃; 0 wt % to about 2.0 wt % CuO; and 0 wt % to about 2.0 wt% V₂O₅.

According to aspect (23), the method of any of aspects (18) to (22) isprovided, wherein the precursor glass-based article comprises: about65.0 wt % to about 75.0 wt % SiO₂; about 7.0 wt % to about 11.0 wt %Al₂O₃; about 6.0 wt % to about 11.0 wt % Li₂O; about 2.0 wt % to about4.0 wt % TiO₂; about 1.5 wt % to about 2.5 wt % P₂O₅; about 2.0 wt % toabout 4.0 wt % ZrO₂; about 1.0 wt % to about 4.0 wt % FeO+Fe₂O₃; about0.5 wt % to about 1.5 wt % NiO; and about 0.1 wt % to about 0.4 wt %Co₃O₄.

According to aspect (24), a glass is provided. The glass comprises:about 55.0 wt % to about 75.0 wt % SiO₂; about 2.0 wt % to about 20.0 wt% Al₂O₃; 0 wt % to about 5.0 wt % B₂O₃; about 5.0 wt % to about 15.0 wt% Li₂O; 0 wt % to about 5.0 wt % Na₂O; 0 wt % to about 4.0 wt % K₂O; 0wt % to about 8.0 wt % MgO; 0 wt % to about 10.0 wt % ZnO; about 0.5 wt% to about 5.0 wt % A TiO₂; about 1.0 wt % to about 6.0 wt % A P₂O₅;about 2.0 wt % to about 10.0 wt % ZrO₂; 0 wt % to about 0.4 wt % CeO₂;about 0.05 wt % to about 0.5 wt % SnO+SnO₂; about 0.1 wt % to about 5.0wt % A FeO+Fe₂O₃; about 0.1 wt % to about 5.0 wt % A NiO; about 0.1 wt %to about 5.0 wt % Co₃O₄; 0 wt % to about 4.0 wt % MnO+MnO₂+Mn₂O₃; 0 wt %to about 2.0 wt % A Cr₂O₃; 0 wt % to about 2.0 wt % A CuO; and 0 wt % toabout 2.0 wt % A V₂O₅.

According to aspect (25), the glass of aspect (24) is provided,comprising: about 65.0 wt % to about 75.0 wt % A SiO₂; about 7.0 wt % toabout 11.0 wt % Al₂O₃; about 6.0 wt % to about 11.0 wt % Li₂O; about 2.0wt % to about 4.0 wt % TiO₂; about 1.5 wt % to about 2.5 wt % P₂O₅;about 2.0 wt % to about 4.0 wt % ZrO₂; about 1.0 wt % to about 4.0 wt %FeO+Fe₂O₃; about 0.5 wt % to about 1.5 wt % NiO; and about 0.1 wt % toabout 0.4 wt % Co₃O₄.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the art from that description or recognized by practicing theembodiments described herein, including the detailed description whichfollows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein and, together with the description, serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically depicts a cross section of a glass ceramic havingcompressive stress layers on surfaces thereof according to embodimentsdisclosed and described herein;

FIG. 2A is a plan view of an exemplary electronic device incorporatingany of the glass ceramics disclosed herein;

FIG. 2B is a perspective view of the exemplary electronic device of FIG.2A;

FIG. 3 is a transmittance spectrum of a glass ceramic having a thicknessof 0.8 mm according to embodiments and two glass ceramics having athickness of 0.8 mm according to comparative examples;

FIG. 4 is a Weibull plot of the results of a Ring-on-Ring (RoR) strengthtest for a glass ceramic according to an embodiment before and after anion exchange treatment;

FIG. 5 is an plot of the concentration in wt % of Na₂O as a function ofdepth from a surface of an ion exchanged glass ceramic according to anembodiment, as measured by electron microprobe;

FIG. 6 is a schematic depiction of a ring-on-ring testing apparatus.

DETAILED DESCRIPTION

Reference will now be made in detail to black lithium silicate glassceramics according to various embodiments. In particular, the blacklithium silicate glass ceramics have a pleasing appearance, and exhibithigh strength and fracture toughness. Therefore, the black lithiumsilicate glass ceramics are suited for use as housings in portableelectronic devices.

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. Whenever agroup is described as consisting of at least one of a group of elementsor combinations thereof, it is understood that the group may consist ofany number of those elements recited, either individually or incombination with each other. Unless otherwise specified, a range ofvalues, when recited, includes both the upper and lower limits of therange as well as any ranges therebetween. As used herein, the indefinitearticles “a,” “an,” and the corresponding definite article “the” mean“at least one” or “one or more,” unless otherwise specified. It also isunderstood that the various features disclosed in the specification andthe drawings can be used in any and all combinations.

Unless otherwise specified, all compositions of the glasses describedherein are expressed in terms of weight percent (wt %), and theconstituents are provided on an oxide basis. Unless otherwise specified,all temperatures are expressed in terms of degrees Celsius (° C.).

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. For example, a glass that is “substantiallyfree of K₂O” is one in which K₂O is not actively added or batched intothe glass, but may be present in very small amounts as a contaminant,such as in amounts of less than about 0.01 wt %. As utilized herein,when the term “about” is used to modify a value, the exact value is alsodisclosed.

The glass ceramics contain a primary crystal phase, a secondary crystalphase, and a residual glass phase. The primary crystal phase is thepredominant crystal phase, defined herein as the crystal phase thataccounts for the largest fraction of the glass ceramic by weight.Accordingly, the secondary crystal phase is present in a concentrationin terms of weight percent of the glass ceramic that is less than theweight percent of the primary crystal phase.

In embodiments, the primary crystal phase includes lithium silicate. Thelithium silicate may be lithium metasilicate or lithium disilicate. Inembodiments, the lithium silicate is the only primary crystal phase.

In some embodiments, the glass ceramic includes a secondary crystalphase including at least one of petalite, β-quartz, β-spodumene,cristobalite, and lithium phosphate. As utilized herein, β-spodumene mayrefer to β-spodumene solid solutions. In embodiments, the glass ceramiccontains more than one secondary crystal phase. In some embodiments,additional crystal phases may be present in the glass ceramic.

In embodiments, the total crystallinity of the glass ceramic is highenough to provide enhanced mechanical properties, such as hardness,Young's modulus, and scratch resistance. As utilized herein, the totalcrystallinity is provided in wt % and refers to the sum of the wt % ofall the crystal phases present in the glass ceramic. In embodiments, thetotal crystallinity is greater than or equal to about 50 wt %, such asgreater than or equal to about 55 wt %, greater than or equal to about60 wt %, greater than or equal to about 65 wt %, greater than or equalto about 70 wt %, greater than or equal to about 75 wt %, or more. Itshould be understood that, in embodiments, any of the above ranges maybe combined with any other range. In embodiments, the totalcrystallinity of the glass ceramic is from greater than or equal toabout 50 wt % to less than or equal to about 75 wt %, such as greaterthan or equal to about 55 wt % to less than or equal to about 70 wt %,or greater than or equal to about 60 wt % to less than or equal to about65 wt %, and all ranges and sub-ranges between the foregoing values. Thetotal crystallinity of the glass ceramic is determined through Rietveldquantitative analysis of X-ray diffraction (XRD) results.

The glass ceramics are opaque or translucent. In embodiments, the glassceramics exhibit a transmittance of less than about 10% in the visiblerange (380 nm to 760 nm), such as less than about 9%, less than about8%, less than about 7%, less than about 6%, less than about 5%, lessthan about 4%, less than about 3%, less than about 2%, less than about1%, or less. The transmittance as utilized herein refers to totaltransmittance, and is measured using a Perkin Elmer Lambda 950UV/Vis/NIR spectrophotometer with a 150 mm integrating sphere. Thesamples are mounted at the sphere's entrance port, which allows for thecollection of wide angle scattered light, and a reference Spectralonreflectance disc is located over the sphere's exit port. The totaltransmittance is generated relative to an open beam baselinemeasurement.

In embodiments, the glass ceramics are black. The glass ceramics may becharacterized by the following color coordinates: L* 20.0 to 40.0, a*−1.0 to 0.5, and b* −5.0 to 1.0. In some embodiments, the L* value ofthe glass ceramic may be from 20.0 to 40.0, such as from 21.0 to 39.0,from 22.0 to 38.0, from 23.0 to 37.0, from 24.0 to 36.0, from 23.0 to35.0, from 25.0 to 34.0, from 26.0 to 33.0, from 27.0 to 32.0, from 28.0to 31.0, or from 29.0 to 30.0%, and all ranges and sub-ranges betweenthe foregoing values. In some embodiments, the a* value of the glassceramic may be from −1.0 to 1.0, such as from −0.9 to 0.9, from −0.8 to0.8, from −0.7 to 0.7, from −0.6 to 0.6, from −0.5 to 0.5, from −0.4 to0.4, from −0.3 to 0.3, from −0.2 to 0.2, or from −0.1 to 0.1, and allranges and sub-ranges between the foregoing values. In some embodiments,the b* value of the glass ceramic may be from −5.0 to 2.0, such as from−4.5 to 1.5, from −4.0 to 1.0, from −3.5 to 0.5, from −3.0 to 0.0, from−2.5 to −0.5, from −2.0 to −1.0, or −1.5, and all ranges and sub-rangesbetween the foregoing values. As utilized herein, the color coordinatesare measured using an X-rite Ci7 F02 illuminant under SCI UVCconditions.

In embodiments, the glass ceramic may have a high fracture toughness.The high fracture toughness is achieved at least in part due to thecrystal phase assemblage of the glass ceramic. In some embodiments, theglass ceramic may have a fracture toughness of greater than or equal toabout 0.9 MPa·m^(0.5) to less than or equal to about 2.0 MPa·m^(0.5),such as greater than or equal to about 1.0 MPa·m^(0.5) to less than orequal to about 1.9 MPa·m^(0.5), greater than or equal to about 1.1MPa·m^(0.5) to less than or equal to about 1.8 MPa·m^(0.5), greater thanor equal to about 1.2 MPa·m^(0.5) to less than or equal to about 1.7MPa·m^(0.5), greater than or equal to about 1.3 MPa·m^(0.5) to less thanor equal to about 1.6 MPa·m^(0.5), greater than or equal to about 1.4MPa·m^(0.5) to less than or equal to about 1.5 MPa·m^(0.5), and allranges and sub-ranges between the foregoing values. In some embodiments,the glass ceramic may have a fracture toughness of greater than or equalto about 1.0 MPa·m^(0.5) to less than or equal to about 1.5 MPa·m^(0.5).The fracture toughness is measured by chevron notched short bar (CNSB)method, as described below.

In embodiments, the glass ceramic may have a high strength. The highstrength is achieved at least in part due to the crystal phaseassemblage of the glass ceramic. In some embodiments, the glass ceramichas a strength of greater than or equal to about 290 MPa, such asgreater than or equal to about 300 MPa, greater than or equal to about310 MPa, greater than or equal to about 320 MPa, greater than or equalto about 330 MPa, greater than or equal to about 340 MPa, greater thanor equal to about 350 MPa, greater than or equal to about 360 MPa,greater than or equal to about 370 MPa, greater than or equal to about380 MPa, greater than or equal to about 390 MPa, or more. Inembodiments, the glass ceramic has a strength of greater than or equalto about 290 MPa to less than or equal to about 400 MPa, such as greaterthan or equal to about 300 MPa to less than or equal to about 390 MPa,greater than or equal to about 310 MPa to less than or equal to about380 MPa, greater than or equal to about 320 MPa to less than or equal toabout 370 MPa, greater than or equal to about 330 MPa to less than orequal to about 360 MPa, greater than or equal to about 340 MPa to lessthan or equal to about 350 MPa, and any and all sub-ranges formed fromthese endpoints. The strength refers to the strength as measured by thering-on-ring test described below.

The composition of the lithium silicate glass ceramics will now bedescribed. In embodiments of glass ceramics described herein, theconcentration of constituent components (e.g., SiO₂, Al₂O₃, Li₂O, Na₂Oand the like) are given in weight percent (wt %) on an oxide basis,unless otherwise specified. Components of the glass ceramics accordingto embodiments are discussed individually below. It should be understoodthat any of the variously recited ranges of one component may beindividually combined with any of the variously recited ranges for anyother component.

In embodiments of the glass ceramics disclosed herein, SiO₂ is thelargest constituent. The SiO₂ acts as the primary network former andstabilizes the network structure. The SiO₂ is necessary for theformation of the desired lithium silicate crystal phase. Pure SiO₂ has arelatively low CTE and is alkali free. However, pure SiO₂ has a highmelting point. Accordingly, if the concentration of SiO₂ in the glassceramic is too high, the formability of the precursor glass compositionused to form the glass ceramics may be diminished as higherconcentrations of SiO₂ increase the difficulty of melting the glass,which, in turn, adversely impacts the formability of the precursorglass. In embodiments, the glass composition generally comprises SiO₂ inan amount greater than or equal to about 55.0 wt %, such as greater thanor equal to about 56.0 wt %, greater than or equal to about 57.0 wt %,greater than or equal to about 58.0 wt %, greater than or equal to about59.0 wt %, greater than or equal to about 60.0 wt %, greater than orequal to about 61.0 wt %, greater than or equal to about 62.0 wt %,greater than or equal to about 63.0 wt %, greater than or equal to about64.0 wt %, greater than or equal to about 65.0 wt %, greater than orequal to about 66.0 wt %, greater than or equal to about 67.0 wt %,greater than or equal to about 68.0 wt %, greater than or equal to about69.0 wt %, greater than or equal to about 70.0 wt %, greater than orequal to about 71.0 wt %, greater than or equal to about 72.0 wt %,greater than or equal to about 73.0 wt %, or greater than or equal toabout 74.0 wt %. In embodiments, the glass composition comprises SiO₂ inamounts less than or equal to about 75.0 wt %, such as less than orequal to about 74.0 wt %, less than or equal to about 73.0 wt %, lessthan or equal to about 72.0 wt %, or less than or equal to about 71.0 wt%, less than or equal to about 70.0 wt %, less than or equal to about69.0 wt %, less than or equal to about 68.0 wt %, less than or equal toabout 67.0 wt %, less than or equal to about 66.0 wt %, less than orequal to about 65.0 wt %, less than or equal to about 64.0 wt %, lessthan or equal to about 63.0 wt %, less than or equal to about 62.0 wt %,less than or equal to about 61.0 wt %, less than or equal to about 60.0wt %, less than or equal to about 59.0 wt %, less than or equal to about58.0 wt %, less than or equal to about 57.0 wt %, or less than or equalto about 56.0 wt %. It should be understood that, in embodiments, any ofthe above ranges may be combined with any other range. In embodiments,the glass composition comprises SiO₂ in an amount from greater than orequal to about 55.0 wt % to less than or equal to about 75.0 wt %, suchas from greater than or equal to about 56.0 wt % to less than or equalto about 74.0 wt %, from greater than or equal to about 57.0 wt % toless than or equal to about 73.0 wt %, from greater than or equal toabout 58.0 wt % to less than or equal to about 72.0 wt %, from greaterthan or equal to about 59.0 wt % to less than or equal to about 71.0 wt%, from greater than or equal to about 60.0 wt % to less than or equalto about 70.0 wt %, from greater than or equal to about 61.0 wt % toless than or equal to about 69.0 wt %, from greater than or equal toabout 62.0 wt % to less than or equal to about 68.0 wt %, from greaterthan or equal to about 63.0 wt % to less than or equal to about 67.0 wt%, from greater than or equal to about 64.0 wt % to less than or equalto about 66.0 wt %, or about 65.0 wt %, and all ranges and sub-rangesbetween the foregoing values. In some embodiments, the glass ceramicincludes SiO₂ in an amount from greater than or equal to about 65 wt %to less than or equal to about 75 wt %.

The glass ceramics of embodiments may further comprise Al₂O₃. Al₂O₃ mayincrease the viscosity of the precursor glass compositions used to formthe glass ceramics due to its tetrahedral coordination in a glass meltformed from a glass composition, decreasing the formability of the glasscomposition when the amount of Al₂O₃ is too high. However, when theconcentration of Al₂O₃ is balanced against the concentration of SiO₂ andthe concentration of alkali oxides in the glass composition, Al₂O₃ canreduce the liquidus temperature of the glass melt, thereby enhancing theliquidus viscosity and improving the compatibility of the glasscomposition with certain forming processes, such as the fusion formingprocess. However, if the Al₂O₃ content is too high, the amount oflithium disilicate crystals formed in the glass ceramic may beundesirably decreased, preventing the formation of an interlockingstructure. Similarly to the SiO_(2,) the Al₂O₃ stabilizes the networkstructure. In embodiments, the glass composition generally comprisesAl₂O₃ in a concentration of greater than or equal to about 2.0 wt %,such as greater than or equal to about 3.0 wt %, greater than or equalto about 4.0 wt %, greater than or equal to about 5.0 wt %, greater thanor equal to about 6.0 wt %, greater than or equal to about 7.0 wt %,greater than or equal to about 8.0 wt %, greater than or equal to about9.0 wt %, greater than or equal to about 10.0 wt %, greater than orequal to about 11.0 wt %, greater than or equal to about 12.0 wt %,greater than or equal to about 13.0 wt %, greater than or equal to about14.0 wt %, greater than or equal to about 15.0 wt %, greater than orequal to about 16.0 wt %, greater than or equal to about 17.0 wt %,greater than or equal to about 18.0 wt %, or greater than or equal toabout 19.0 wt %. In embodiments, the glass composition comprises Al₂O₃in amounts less than or equal to about 20.0 wt %, such as less than orequal to about 19.0 wt %, less than or equal to about 18.0 wt %, lessthan or equal to about 17.0 wt %, less than or equal to about 16.0 wt %,less than or equal to about 15.0 wt %, less than or equal to about 14.0wt %, less than or equal to about 13.0 wt %, less than or equal to about12.0 wt %, less than or equal to about 11.0 wt %, less than or equal toabout 10.0 wt %, less than or equal to about 9.0 wt %, less than orequal to about 8.0 wt %, less than or equal to about 7.0 wt %, less thanor equal to about 6.0 wt %, less than or equal to about 5.0 wt %, lessthan or equal to about 4.0 wt %, or less than or equal to about 3.0 wt%. It should be understood that, in embodiments, any of the above rangesmay be combined with any other range. In other embodiments, the glasscomposition comprises Al₂O₃ in an amount from greater than or equal toabout 2.0 wt % to less than or equal to about 20.0 wt %, such as fromgreater than or equal to about 3.0 wt % to less than or equal to about19.0 wt %, from greater than or equal to about 4.0 wt % to less than orequal to about 18.0 wt %, from greater than or equal to about 5.0 wt %to less than or equal to about 17.0 wt %, from greater than or equal toabout 6.0 wt % to less than or equal to about 16.0 wt %, from greaterthan or equal to about 7.0 wt % to less than or equal to about 15.0 wt%, from greater than or equal to about 8.0 wt % to less than or equal toabout 14.0 wt %, from greater than or equal to about 9.0 wt % to lessthan or equal to about 13.0 wt %, from greater than or equal to about10.0 wt % to less than or equal to about 12.0 wt %, or about 11 wt %,and all ranges and sub-ranges between the foregoing values. Inembodiments, the glass composition comprises Al₂O₃ in an amount fromgreater than or equal to about 7.0 wt % to less than or equal to about11.0 wt %.

The glass ceramics of embodiments may further comprise B₂O₃. Theinclusion of B₂O₃ reduces the melting temperature of the glasscomposition. Additionally, the existence of B₂O₃ in the trigonalcoordination state opens up the structure of the glass composition,allowing the glasses to tolerate some degree of deformation before crackformation occurs. In embodiments, the glass composition contains B₂O₃ inan amount greater than or equal to 0 wt %, such as greater than or equalto about 0.5 wt %, greater than or equal to about 1.0 wt %, greater thanor equal to about 1.5 wt %, greater than or equal to about 2.0 wt %,greater than or equal to about 2.5 wt %, greater than or equal to about3.0 wt %, greater than or equal to about 3.5 wt %, greater than or equalto about 4.0 wt %, or greater than or equal to about 4.5 wt %. Inembodiments, the glass composition contains B₂O₃ in an amount less thanor equal to about 5.0 wt %, such as less than or equal to about 4.5 wt%, less than or equal to about 4.0 wt %, less than or equal to about 3.5wt %, less than or equal to about 3.0 wt %, less than or equal to about2.5 wt %, less than or equal to about 2.0 wt %, less than or equal toabout 1.5 wt %, less than or equal to about 1.0 wt %, or less than orequal to about 0.5 wt %. It should be understood that, in embodiments,any of the above ranges may be combined with any other range. Inembodiments, the glass composition comprises B₂O₃ in an amount fromgreater than or equal to about 0 wt % to less than or equal to about 5.0wt %, such as greater than or equal to about 0.5 wt % to less than orequal to about 4.5 wt %, greater than or equal to about 1.0 wt % to lessthan or equal to about 4.0 wt %, greater than or equal to about 1.5 wt %to less than or equal to about 3.5 wt %, greater than or equal to about2.0 wt % to less than or equal to about 3.0 wt %, or about 2.5 wt %, andall ranges and sub-ranges between the foregoing values.

The glass ceramics of embodiments further comprise Li₂O. The addition oflithium in the glass ceramic allows for an ion exchange process andfurther reduces the softening point of the precursor glass composition.The Li₂O also provides the lithium necessary for the formation of thelithium silicate crystal phase when the precursor glass is cerammed toform a glass ceramic. If the Li₂O content is too high, the forming ofthe precursor glass becomes difficult. In embodiments, the glasscomposition generally comprises Li₂O in an amount greater than 5.0 wt %,such as greater than or equal to about 5.5 wt %, greater than or equalto about 6.0 wt %, greater than or equal to about 6.5 wt %, greater thanor equal to about 7.0 wt %, greater than or equal to about 7.5 wt %,greater than or equal to about 8.0 wt %, greater than or equal to about8.5 wt %, greater than or equal to about 9.0 wt %, greater than or equalto about 9.5 wt %, greater than or equal to about 10.0 wt %, greaterthan or equal to about 10.5 wt %, greater than or equal to about 11.0 wt%, greater than or equal to about 11.5 wt %, greater than or equal toabout 12.0 wt %, greater than or equal to about 12.5 wt %, greater thanor equal to about 13.0 wt %, greater than or equal to about 13.5 wt %,greater than or equal to about 14.0 wt %, or greater than or equal toabout 14.5 wt %. In some embodiments, the glass composition comprisesLi₂O in amounts less than or equal to about 15.0 wt %, such as less thanor equal to about 14.5 wt %, less than or equal to about 14.0 wt %, lessthan or equal to about 13.5 wt %, less than or equal to about 13.0 wt %,less than or equal to about 12.5 wt %, less than or equal to about 12.0wt %, less than or equal to about 11.5 wt %, less than or equal to about11.0 wt %, less than or equal to about 10.5 wt %, less than or equal toabout 10.0 wt %, less than or equal to about 9.5 wt %, less than orequal to about 9.0 wt %, less than or equal to about 8.5 wt %, less thanor equal to about 8.0 wt %, less than or equal to about 7.5 wt %, lessthan or equal to about 7.0 wt %, less than or equal to about 6.5 wt %,less than or equal to about 6.0 wt %, or less than or equal to about 5.5wt %. It should be understood that, in embodiments, any of the aboveranges may be combined with any other range. In embodiments, the glasscomposition comprises Li₂O in an amount from greater than 5.0 wt % toless than or equal to about 15.0 wt %, such as from greater than orequal to about 5.5 wt % to less than or equal to about 14.5 wt %, fromgreater than or equal to about 6.0 wt % to less than or equal to about14.0 wt %, from greater than or equal to about 6.5 wt % to less than orequal to about 13.5 wt %, from greater than or equal to about 7.0 wt %to less than or equal to about 13.0 wt %, from greater than or equal toabout 7.5 wt % to less than or equal to about 12.5 wt %, from greaterthan or equal to about 8.0 wt % to less than or equal to about 12.0 wt%, from greater than or equal to about 8.5 wt % to less than or equal toabout 11.5 wt %, from greater than or equal to about 9.0 wt % to lessthan or equal to about 11.0 wt %, from greater than or equal to about9.5 wt % to less than or equal to about 10.5 wt %, or about 10 wt %, andall ranges and sub-ranges between the foregoing values. In someembodiments, the glass composition comprises Li₂O in an amount fromgreater than or equal to about 6.0 wt % to less than or equal to about11.0 wt % or from greater than or equal to about 7 wt % to less than orequal to about 15 wt %.

The glass ceramic may include one or more alkali metal oxides inaddition to Li₂O. The alkali metal oxides further facilitate thechemical strengthening of the glass ceramic, such as through an ionexchange process. The alkali metal oxides (e.g., Li₂O, Na₂O, and K₂O aswell as other alkali metal oxides including Cs₂O and Rb₂O) in the glassceramic may be referred to as “R₂O”, and the content of R₂O may beexpressed in wt %. In some embodiments, the glass ceramic may include amixture of alkali metal oxides, such as a combination of Li₂O and Na₂O,a combination of Li₂O and K₂O, or a combination of Li₂O, Na₂O, and K₂O.The inclusion of a mixture of alkali metal oxides in the glass ceramicmay result in faster and more efficient ion exchange.

The glass ceramic may include Na₂O as an additional alkali metal oxide.The Na₂O aids in the ion exchangeability of the glass ceramic, and alsodecreases the melting point of the precursor glass composition andimproves formability of the precursor glass composition. The presence ofNa₂O also shortens the length of the necessary ceramming treatment.However, if too much Na₂O is added to the glass composition, the CTE maybe too high. The Na₂O may also reduce the viscosity of the residualglass in the glass ceramic, which may reduce the cracks formed in theglass ceramics during the ceramming treatment. In embodiments, the glasscomposition generally comprises Na₂O in an amount greater than or equalto 0.0 wt %, such as greater than or equal to about 0.5 wt %, greaterthan or equal to about 1.0 wt %, greater than or equal to about 1.5 wt%, greater than or equal to about 2.0 wt %, greater than or equal toabout 2.5 wt %, greater than or equal to about 3.0 wt %, greater than orequal to about 3.5 wt %, greater than or equal to about 4.0 wt %, orgreater than or equal to about 4.5 wt %. In some embodiments, the glasscomposition comprises Na₂O in amounts less than or equal to about 5.0 wt%, such as less than or equal to about 4.5 wt %, less than or equal toabout 4.0 wt %, less than or equal to about 3.5 wt %, less than or equalto about 3.0 wt %, less than or equal to about 2.5 wt %, less than orequal to about 2.0 wt %, less than or equal to about 1.5 wt %, less thanor equal to about 1.0 wt %, or less than or equal to about 0.5 wt %. Itshould be understood that, in embodiments, any of the above ranges maybe combined with any other range. In embodiments, the glass compositioncomprises Na₂O in an amount from greater than or equal to 0.0 wt % toless than or equal to about 5.0 wt %, such as from greater than or equalto about 0.5 wt % to less than or equal to about 4.5 wt %, from greaterthan or equal to about 1.0 wt % to less than or equal to 4.0 wt %, fromgreater than or equal to about 1.5 wt % to less than or equal to about3.5 wt %, from greater than or equal to about 2.0 wt % to less than orequal to about 3.0 wt %, or about 2.5 wt %, and all ranges andsub-ranges between the foregoing values.

In embodiments, the glass ceramic may include P₂O₅. The P₂O₅ acts as anucleating agent to produce bulk nucleation. If the concentration ofP₂O₅ is too low, the precursor glass may not crystallize or may undergoundesired surface crystallization. If the concentration of P₂O₅ is toohigh, devitrification of the precursor glass upon cooling during formingmay be difficult to control. The presence of P₂O₅ in the glass ceramicmay also increase the diffusivity of metal ions in the glass ceramic,which may increase the efficiency of ion exchanging the glass ceramic.In embodiments, the amount of P₂O₅ in the glass ceramic may be greaterthan or equal to about 1.0 wt %, such as greater than or equal to about1.5 wt %, greater than or equal to about 2.0 wt %, greater than or equalto about 2.5 wt %, greater than or equal to about 3.0 wt %, greater thanor equal to about 3.5 wt %, greater than or equal to about 4.0 wt %,greater than or equal to about 4.5 wt %, greater than or equal to about5.0 wt %, or greater than or equal to about 5.5 wt %. In embodiments,the amount of P₂O₅ in the glass ceramic may be less than or equal toabout 6.0 wt %, such as less than or equal to about 5.5 wt %, less thanor equal to about 5.0 wt %, less than or equal than about 4.5 wt %, lessthan or equal to about 4.0 wt %, less than or equal to about 3.5 wt %,less than or equal to about 3.0 wt %, less than or equal to about 2.5 wt%, less than or equal to about 2.0 wt %, or less than or equal to about1.5 wt %. It should be understood that, in embodiments, any of the aboveranges may be combined with any other range. In embodiments, the glasscomposition comprises P₂O₅ in an amount from greater than or equal toabout 1.0 wt % to less than or equal to about 6.0 wt %, such as fromgreater than or equal to about 1.5 wt % to less than or equal to about5.5 wt %, from greater than or equal to about 2.0 wt % to less than orequal to about 5.0 wt %, from greater than or equal to about 2.5 wt % toless than or equal to about 4.5 wt %, from greater than or equal toabout 3.0 wt % to less than or equal to about 4.0 wt %, or about 4.0 wt%, and all ranges and sub-ranges between the foregoing values.

In embodiments, the glass ceramic may include ZrO₂. The ZrO₂ acts as anetwork former or intermediate in the precursor glass compositions. TheZrO₂ increases the stability of the glass compositions by reducing thedevitrification of the glass composition during forming, and alsoreduces the liquidus temperature. The addition of ZrO₂ also increasesthe chemical durability of the glass ceramics, and increases the elasticmodulus of the residual glass. In embodiments, the amount of ZrO₂ in theglass ceramic is greater than or equal to about 2.0 wt %, such asgreater than or equal to about 2.5 wt %, greater than or equal to about3.0 wt %, greater than or equal to about 3.5 wt %, greater than or equalto about 4.0 wt %, greater than or equal to about 4.5 wt %, greater thanor equal to about 5.0 wt %, greater than or equal to about 5.5 wt %,greater than or equal to about 6.0 wt %, greater than or equal to about6.5 wt %, greater than or equal to about 7.0 wt %, greater than or equalto about 7.5 wt %, greater than or equal to about 8.0 wt %, greater thanor equal to about 8.5 wt %, greater than or equal to about 9.0 wt %, orgreater than or equal to about 9.5 wt %. In embodiments, the amount ofZrO₂ in the glass ceramic is less than or equal to about 10.0 wt %, suchas less than or equal to about 9.5 wt %, less than or equal to about 9.0wt %, less than or equal to about 8.5 wt %, less than or equal to about8.0 wt %, less than or equal to about 7.5 wt %, less than or equal toabout 7.0 wt %, less than or equal to about 6.5 wt %, less than or equalto about 6.0 wt %, less than or equal to about 5.5 wt %, less than orequal to about 5.0 wt %, less than or equal than about 4.5 wt %, lessthan or equal to about 4.0 wt %, less than or equal to about 3.5 wt %,less than or equal to about 3.0 wt %, or less than or equal to about 2.5wt %. It should be understood that, in embodiments, any of the aboveranges may be combined with any other range. In embodiments, the amountof ZrO₂ in the glass ceramic is greater than or equal to about 2.0 wt %to less than or equal to about 10.0 wt %, such as greater than or equalto about 2.5 wt % to less than or equal to about 9.5 wt %, greater thanor equal to about 3.0 wt % to less than or equal to about 9.0 wt %,greater than or equal to about 3.5 wt % to less than or equal to about8.5 wt %, greater than or equal to about 4.0 wt % to less than or equalto about 8.0 wt %, greater than or equal to about 4.5 wt % to less thanor equal to about 7.5 wt %, greater than or equal to about 5.0 wt % toless than or equal to about 7.0 wt %, greater than or equal to about 5.5wt % to less than or equal to about 6.5 wt %, or about 6.0 wt %, and allranges and sub-ranges between the foregoing values. In some embodiments,the amount of ZrO₂ in the glass ceramic is greater than or equal toabout 2.0 wt % to less than or equal to about 4.0 wt %.

The glass ceramics of embodiments may further comprise ZnO. The ZnO inthe precursor glass supplies the zinc necessary to form the gahnitecrystal phase when the precursor glass is cerammed to form a glassceramic. The ZnO also acts as a flux, lowering the cost of theproduction of the precursor glass. In the glass ceramic, the ZnO may bepresent in petalite crystals as a solid solution. In embodiments, theglass composition generally comprises ZnO in a concentration of greaterthan or equal to about 0.0 wt %, such as greater than or equal to about0.5 wt %, greater than or equal to about 1.0 wt %, greater than or equalto about 1.5 wt %, greater than or equal to about 2.0 wt %, greater thanor equal to about 2.5 wt %, greater than or equal to about 3.0 wt %,greater than or equal to about 3.5 wt %, greater than or equal to about4.0 wt %, greater than or equal to about 4.5 wt %, greater than or equalto about 5.0 wt %, greater than or equal to about 5.5 wt %, greater thanor equal to about 6.0 wt %, greater than or equal to about 6.5 wt %,greater than or equal to about 7.0 wt %, greater than or equal to about7.5 wt %, greater than or equal to about 8.0 wt %, greater than or equalto about 8.5 wt %, greater than or equal to about 9.0 wt %, or greaterthan or equal to about 9.5 wt %. In embodiments, the glass compositioncomprises ZnO in amounts less than or equal to about 10.0 wt %, such asless than or equal to about 9.5 wt %, less than or equal to about 9.0 wt%, less than or equal to about 8.5 wt %, less than or equal to about 8.0wt %, less than or equal to about 7.5 wt %, less than or equal to about7.0 wt %, less than or equal to about 6.5 wt %, less than or equal toabout 6.0 wt %, less than or equal to about 5.5 wt %, less than or equalto about 5.0 wt %, less than or equal than about 4.5 wt %, less than orequal to about 4.0 wt %, less than or equal to about 3.5 wt %, less thanor equal to about 3.0 wt %, less than or equal to about 2.5 wt %, lessthan or equal to about 2.0 wt %, less than or equal to about 1.5 wt %,less than or equal to about 1.0 wt %, or less than or equal to about 0.5wt %. It should be understood that, in embodiments, any of the aboveranges may be combined with any other range. In embodiments, the glasscomposition comprises ZnO in an amount from greater than or equal toabout 0.0 wt % to less than or equal to about 10.0 wt %, such as fromgreater than or equal to about 0.5 wt % to less than or equal to about9.5 wt %, from greater than or equal to about 1.0 wt % to less than orequal to about 9.0 wt %, from greater than or equal to about 1.5 wt % toless than or equal to about 8.5 wt %, from greater than or equal toabout 2.0 wt % to less than or equal to about 8.0 wt %, from greaterthan or equal to about 2.5 wt % to less than or equal to about 7.5 wt %,from greater than or equal to about 3.0 wt % to less than or equal toabout 7.0 wt %, from greater than or equal to about 3.5 wt % to lessthan or equal to about 6.5 wt %, from greater than or equal to about 4.0wt % to less than or equal to about 6.0 wt %, from greater than or equalto about 4.5 wt % to less than or equal to about 5.5 wt %, or about 5.0wt %, and all ranges and sub-ranges between the foregoing values. Inembodiments, the glass ceramic may be substantially free or free of ZnO.

The glass ceramics of embodiments may further comprise MgO. The presenceof MgO in the glass may increase the elastic modulus. The MgO also actsas a flux, lowering the cost of the production of the precursor glass.In the glass ceramic, the MgO may be present in petalite crystals as asolid solution. In embodiments, the amount of MgO in the glass ceramicis greater than or equal to about 0.0 wt %, such as greater than orequal to about 0.5 wt %, greater than or equal to about 1.0 wt %,greater than or equal to about 1.5 wt %, greater than or equal to about2.0 wt %, greater than or equal to about 2.5 wt %, greater than or equalto about 3.0 wt %, greater than or equal to about 3.5 wt %, greater thanor equal to about 4.0 wt %, greater than or equal to about 4.5 wt %,greater than or equal to about 5.0 wt %, greater than or equal to about5.5 wt %, greater than or equal to about 6.0 wt %, greater than or equalto about 6.5 wt %, greater than or equal to about 7.0 wt %, or greaterthan or equal to about 7.5 wt %. In embodiments, the amount of MgO inthe glass ceramic is less than or equal to about 8.0 wt %, such as lessthan or equal to about 7.5 wt %, less than or equal to about 7.0 wt %,less than or equal to about 6.5 wt %, less than or equal to about 6.0 wt%, less than or equal to about 5.5 wt %, less than or equal to about 5.0wt %, less than or equal than about 4.5 wt %, less than or equal toabout 4.0 wt %, less than or equal to about 3.5 wt %, less than or equalto about 3.0 wt %, less than or equal to about 2.5 wt %, less than orequal to about 2.0 wt %, less than or equal to about 1.5 wt %, less thanor equal to about 1.0 wt %, or less than or equal to about 0.5 wt %. Itshould be understood that, in embodiments, any of the above ranges maybe combined with any other range. In embodiments, the amount of MgO inthe glass ceramic is greater than or equal to about 0.0 wt % to lessthan or equal to about 8.0 wt %, such as from greater than or equal toabout 0.5 wt % to less than or equal to about 7.5 wt %, from greaterthan or equal to about 1.0 wt % to less than or equal to about 7.0 wt %,from greater than or equal to about 1.5 wt % to less than or equal toabout 6.5 wt %, from greater than or equal to about 2.0 wt % to lessthan or equal to about 6.0 wt %, from greater than or equal to about 2.5wt % to less than or equal to about 5.5 wt %, from greater than or equalto about 3.0 wt % to less than or equal to about 5.0 wt %, from greaterthan or equal to about 3.5 wt % to less than or equal to about 4.5 wt %,or about 4.0 wt %, and all ranges and sub-ranges between the foregoingvalues.

The glass ceramics of embodiments may further include TiO₂. The TiO₂ mayact as a nucleating agent and in some cases may act as a colorant. Inembodiments, the glass may include TiO₂ in an amount greater than orequal to about 0.5 wt %, such as greater than or equal to about 1.0 wt%, greater than or equal to about 1.5 wt %, greater than or equal toabout 2.0 wt %, greater than or equal to about 2.5 wt %, greater than orequal to about 3.0 wt %, greater than or equal to about 3.5 wt %,greater than or equal to about 4.0 wt %, or greater than or equal toabout 4.5 wt %. In embodiments, the glass may include TiO₂ in an amountless than or equal to about 5.0 wt %, such as less than or equal toabout 4.5 wt %, less than or equal to about 4.0 wt %, less than or equalto about 3.5 wt %, less than or equal to about 3.0 wt %, or less than orequal to about 2.5 wt %. It should be understood that, in embodiments,any of the above ranges may be combined with any other range. In otherembodiments, the glass may include TiO₂ in an amount from greater thanor equal to about 0.5 wt % to less than or equal to about 5.0 wt %, suchas an amount from greater than or equal to about 1.0 wt % to less thanor equal to about 4.5 wt %, from greater than or equal to about 1.5 wt %to less than or equal to about 4.0 wt %, from greater than or equal toabout 2.0 wt % to less than or equal to about 3.5 wt %, or from greaterthan or equal to about 2.5 wt % to less than or equal to about 3.0 wt %,and all ranges and sub-ranges between the foregoing values.

In embodiments, the glass ceramic may optionally include one or morefining agents. In some embodiments, the fining agents may include, forexample, SnO+SnO₂ and/or As₂O₃. In embodiments, SnO+SnO₂ may be presentin the glass composition in an amount less than or equal to 0.5 wt %,such as from greater than or equal to 0.05 wt % to less than or equal to0.5 wt %, greater than or equal to 0.1 wt % to less than or equal to 0.4wt %, or greater than or equal to 0.2 wt % to less than or equal to 0.3wt %, and all ranges and sub-ranges between the foregoing values. Inembodiments, the glass ceramic may be free or substantially free of oneor both of arsenic and antimony.

The glass ceramic includes colorants to produce the desired black colorand opacity. The colorants may be selected from FeO+Fe₂O₃, NiO, Co₃O₄,TiO₂, MnO+MnO₂+Mn₂O₃, Cr₂O₃, CuO, and/or V₂O₅. In some embodiments, theglass ceramic includes a mixture of FeO+Fe₂O₃, NiO, and Co₃O₄, whichallows the achievement of the desired color space.

In some embodiments, the glass includes FeO and/or Fe₂O₃ such thatFeO+Fe₂O₃ is included in an amount greater than or equal to about 0.1 wt%, such as greater than or equal to about 0.5 wt %, greater than orequal to about 1.0 wt %, greater than or equal to about 1.5 wt %,greater than or equal to about 2.0 wt %, greater than or equal to about3.5 wt %, greater than or equal to about 4.0 wt %, or greater than orequal to about 4.5 wt %. In some embodiments, the glass includesFeO+Fe₂O₃ in an amount of less than or equal to about 5.0 wt %, such asless than or equal to about 4.5 wt %, less than or equal to about 4.0 wt%, less than or equal to about 3.5 wt %, less than or equal to about 3.0wt %, less than or equal to about 2.5 wt %, less than or equal to about2.0 wt %, less than or equal to about 1.5 wt %, less than or equal toabout 1.0 wt %, or less than or equal to about 0.5 wt %. It should beunderstood that, in embodiments, any of the above ranges may be combinedwith any other range. In embodiments, the glass may include FeO+Fe₂O₃ inan amount from greater than or equal to about 0.1 wt % to less than orequal to about 5.0 wt %, such as an amount from greater than or equal toabout 0.5 wt % to less than or equal to about 4.5 wt %, from greaterthan or equal to about 1.0 wt % to less than or equal to about 4.0 wt %,from greater than or equal to about 1.5 wt % to less than or equal toabout 3.5 wt %, from greater than or equal to about 2.0 wt % to lessthan or equal to about 3.0 wt %, or about 2.5 wt %, and all ranges andsub-ranges between the foregoing values. In embodiments, the glass mayinclude FeO+Fe₂O₃ in an amount from greater than or equal to about 1.0wt % to less than or equal to about 4.0 wt %.

In some embodiments, the glass includes NiO in an amount greater than orequal to about 0.1 wt %, such as greater than or equal to about 0.5 wt%, greater than or equal to about 1.0 wt %, greater than or equal toabout 1.5 wt %, greater than or equal to about 2.0 wt %, greater than orequal to about 3.5 wt %, greater than or equal to about 4.0 wt %, orgreater than or equal to about 4.5 wt %. In some embodiments, the glassincludes NiO in an amount of less than or equal to about 5.0 wt %, suchas less than or equal to about 4.5 wt %, less than or equal to about 4.0wt %, less than or equal to about 3.5 wt %, less than or equal to about3.0 wt %, less than or equal to about 2.5 wt %, less than or equal toabout 2.0 wt %, less than or equal to about 1.5 wt %, less than or equalto about 1.0 wt %, or less than or equal to about 0.5 wt %. It should beunderstood that, in embodiments, any of the above ranges may be combinedwith any other range. In embodiments, the glass may include NiO in anamount from greater than or equal to about 0.1 wt % to less than orequal to about 5.0 wt %, such as an amount from greater than or equal toabout 0.5 wt % to less than or equal to about 4.5 wt %, from greaterthan or equal to about 1.0 wt % to less than or equal to about 4.0 wt %,from greater than or equal to about 1.5 wt % to less than or equal toabout 3.5 wt %, from greater than or equal to about 2.0 wt % to lessthan or equal to about 3.0 wt %, or about 2.5 wt %, and all ranges andsub-ranges between the foregoing values. In embodiments, the glass mayinclude NiO in an amount from greater than or equal to about 0.5 wt % toless than or equal to about 1.5 wt %.

In some embodiments, the glass includes Co₃O₄ in an amount greater thanor equal to about 0.1 wt %, such as greater than or equal to about 0.5wt %, greater than or equal to about 1.0 wt %, greater than or equal toabout 1.5 wt %, greater than or equal to about 2.0 wt %, greater than orequal to about 3.5 wt %, greater than or equal to about 4.0 wt %, orgreater than or equal to about 4.5 wt %. In some embodiments, the glassincludes Co₃O₄ in an amount of less than or equal to about 5.0 wt %,such as less than or equal to about 4.5 wt %, less than or equal toabout 4.0 wt %, less than or equal to about 3.5 wt %, less than or equalto about 3.0 wt %, less than or equal to about 2.5 wt %, less than orequal to about 2.0 wt %, less than or equal to about 1.5 wt %, less thanor equal to about 1.0 wt %, or less than or equal to about 0.5 wt %. Itshould be understood that, in embodiments, any of the above ranges maybe combined with any other range. In embodiments, the glass may includeCo₃O₄ in an amount from greater than or equal to about 0.1 wt % to lessthan or equal to about 5.0 wt %, such as an amount from greater than orequal to about 0.5 wt % to less than or equal to about 4.5 wt %, fromgreater than or equal to about 1.0 wt % to less than or equal to about4.0 wt %, from greater than or equal to about 1.5 wt % to less than orequal to about 3.5 wt %, from greater than or equal to about 2.0 wt % toless than or equal to about 3.0 wt %, or about 2.5 wt %, and all rangesand sub-ranges between the foregoing values. In embodiments, the glassmay include Co₃O₄ in an amount from greater than or equal to about 0.1wt % to less than or equal to about 0.4 wt %.

In embodiments, the glass ceramic may include MnO, MnO₂, and/or Mn₂O₃such that MnO+MnO₂+Mn₂O₃ may be included in the glass ceramic in anamount from greater than or equal to 0 wt % to less than or equal toabout 4.0 wt %, such as greater than or equal to about 0.5 wt % to lessthan or equal to about 3.5 wt %, greater than or equal to about 1.0 wt %to less than or equal to about 3.0 wt %, greater than or equal to about1.5 wt % to less than or equal to about 2.5 wt %, or about 2.0 wt %, andall ranges and sub-ranges between the foregoing values. In embodiments,Cr₂O₃ may be included in the glass ceramic in an amount from greaterthan or equal to 0 wt % to less than or equal to about 2.0 wt %, such asgreater than or equal to about 0.5 wt % to less than or equal to about1.5 wt %, or about 1.0 wt %, and all ranges and sub-ranges between theforegoing values. In embodiments, CuO may be included in the glassceramic in an amount from greater than or equal to 0 wt % to less thanor equal to about 2.0 wt %, such as greater than or equal to about 0.5wt % to less than or equal to about 1.5 wt %, or about 1.0 wt %, and allranges and sub-ranges between the foregoing values. In embodiments, V₂O₅may be included in the glass ceramic in an amount from greater than orequal to 0 wt % to less than or equal to about 2.0 wt %, such as greaterthan or equal to about 0.5 wt % to less than or equal to about 1.5 wt %,or about 1.0 wt %, and all ranges and sub-ranges between the foregoingvalues.

From the above, glass ceramics according to embodiments may be formedfrom precursor glass articles formed by any suitable method, such asslot forming, float forming, rolling processes, fusion formingprocesses, etc. A precursor glass article may be characterized by themanner in which it is formed. For instance, where the precursor glassarticle may be characterized as float-formable (i.e., formed by a floatprocess), down-drawable and, in particular, fusion-formable orslot-drawable (i.e., formed by a down draw process such as a fusion drawprocess or a slot draw process).

Some embodiments of the precursor glass articles described herein may beformed by a down-draw process. Down-draw processes produce glassarticles having a uniform thickness that possess relatively pristinesurfaces. Because the average flexural strength of the glass article iscontrolled by the amount and size of surface flaws, a pristine surfacethat has had minimal contact has a higher initial strength. In addition,down drawn glass articles have a very flat, smooth surface that can beused in its final application without costly grinding and polishing.

Some embodiments of the precursor glass articles described herein may beformed by a slot draw process. The slot draw process is distinct fromthe fusion draw method. In slot draw processes, the molten raw materialglass is provided to a drawing tank. The bottom of the drawing tank hasan open slot with a nozzle that extends the length of the slot. Themolten glass flows through the slot/nozzle and is drawn downward as acontinuous glass article and into an annealing region.

The glass ceramics may be formed by ceramming a precursor glass underany suitable conditions. The ceramming cycle includes a nucleation stepand a growth step. In some embodiments, the ceramming cycle may includethree separate heat treatment steps at three separate temperatures.

In embodiments, the nucleation step and the growth step (or cerammingstep) occur at temperatures of greater than or equal to about 500° C.,such as greater than or equal to about 525° C., greater than or equal toabout 550° C., greater than or equal to about 575° C., greater than orequal to about 600° C., greater than or equal to about 625° C., greaterthan or equal to about 650° C., greater than or equal to about 675° C.,greater than or equal to about 700° C., greater than or equal to about725° C., greater than or equal to about 750° C., greater than or equalto about 775° C., greater than or equal to about 800° C., greater thanor equal to about 825° C., greater than or equal to about 850° C., orgreater than or equal to about 875° C. In embodiments, the nucleationstep and the growth step occurs at temperatures of from greater than orequal to about 500° C. to less than or equal to about 900° C., such asgreater than or equal to about 525° C. to less than or equal to about875° C., greater than or equal to about 550° C. to less than or equal toabout 850° C., greater than or equal to about 575° C. to less than orequal to about 825° C., greater than or equal to about 600° C. to lessthan or equal to about 800° C., greater than or equal to about 625° C.to less than or equal to about 775° C., greater than or equal to about650° C. to less than or equal to about 750° C., greater than or equal toabout 675° C. to less than or equal to about 725° C., or about 700° C.,and all ranges and sub-ranges between the foregoing values.

In embodiments, the individual steps of the ceramming cycle extend for atime period greater than or equal to about 1.0 hour, such as greaterthan or equal to about 1.5 hours, greater than or equal to about 2.0hours, greater than or equal to about 2.5 hours, greater than or equalto about 3.0 hours, greater than or equal to about 3.5 hours, greaterthan or equal to about 4.0 hours, greater than or equal to about 4.5hours, greater than or equal to about 5.0 hours, greater than or equalto about 5.5 hours, or greater than or equal to about 6.0 hours, greaterthan or equal to about 6.5 hours, greater than or equal to about 7.0hours, greater than or equal to about 7.5 hours, or greater than orequal to about 8.0 hours. In embodiments, the individual steps of theceramming cycle extend for a time period from greater than or equal toabout 1.0 hour to less than or equal to about 8.0 hours, such as greaterthan or equal to about 1.5 hours to less than or equal to about 7.5hours, greater than or equal to about 2.0 hours to less than or equal toabout 7.0 hours, greater than or equal to about 1.5 hours to less thanor equal to about 6.5 hours, greater than or equal to about 2.0 hours toless than or equal to about 6.0 hours, greater than or equal to about2.5 hours to less than or equal to about 5.5 hours, greater than orequal to about 3.0 hours to less than or equal to about 5.0 hours,greater than or equal to about 3.5 hours to less than or equal to about4.5 hours, or about 4.0 hours, and all ranges and sub-ranges between theforegoing values.

In embodiments, the ceramming cycle extends for a total time periodgreater than or equal to about 1.0 hour, such as greater than or equalto about 1.5 hours, greater than or equal to about 2.0 hours, greaterthan or equal to about 2.5 hours, greater than or equal to about 3.0hours, greater than or equal to about 3.5 hours, greater than or equalto about 4.0 hours, greater than or equal to about 4.5 hours, greaterthan or equal to about 5.0 hours, greater than or equal to about 5.5hours, or greater than or equal to about 6.0 hours, greater than orequal to about 6.5 hours, greater than or equal to about 7.0 hours,greater than or equal to about 7.5 hours, greater than or equal to about8.0 hours, greater than or equal to about 8.5 hours, greater than orequal to about 9.0 hours, greater than or equal to about 9.5 hours,greater than or equal to about 10.0 hours, greater than or equal toabout 10.5 hours, greater than or equal to about 11.0 hours greater thanor equal to about 11.5 hours, greater than or equal to about 12.0 hours,greater than or equal to about 12.5 hours, greater than or equal toabout 13.0 hours, greater than or equal to about 13.5 hours, greaterthan or equal to about 14.0 hours, greater than or equal to about 14.5hours, greater than or equal to about 15.0 hours, or greater than orequal to about 15.5 hours. In embodiments, the ceramming cycle extendsfor a total time period from greater than or equal to about 6 hours toless than or equal to about 16.0 hours, such as greater than or equal toabout 6.5 hours to less than or equal to about 15.5 hours, greater thanor equal to about 7.0 hours to less than or equal to about 15.0 hours,greater than or equal to about 7.5 hours to less than or equal to about14.5 hours, greater than or equal to about 8.0 hours to less than orequal to about 14.0 hours, greater than or equal to about 8.5 hours toless than or equal to about 13.5 hours, greater than or equal to about9.0 hours to less than or equal to about 13.0 hours, greater than orequal to about 9.5 hours to less than or equal to about 12.5 hours,greater than or equal to about 10.0 hours to less than or equal to about12.0 hours, greater than or equal to about 10.5 hours to less than orequal to about 11.5 hours, or about 11.0 hours, and all ranges andsub-ranges between the foregoing values.

In embodiments, the precursor glass articles and/or nucleated articlesmay be machined to form a substantially final geometry part prior tobeing cerammed. The machining may include the formation of slots, holes,and regions with varying thickness. In embodiments, the glass may havean engineered edge profile and/or a three-dimensional shape.

In embodiments, the glass ceramics are also chemically strengthened,such as by ion exchange, producing a glass ceramic that is damageresistant for applications such as, but not limited to electronic devicehousings. With reference to FIG. 1, the glass ceramic has a first regionunder compressive stress (e.g., first and second compressive layers 120,122 in FIG. 1) extending from the surface to a depth of compression(DOC) of the glass ceramic and a second region (e.g., central region 130in FIG. 1) under a tensile stress or central tension (CT) extending fromthe DOC into the central or interior region of the glass ceramic. Asused herein, DOC refers to the depth at which the stress within theglass ceramic changes from compressive to tensile. At the DOC, thestress crosses from a positive (compressive) stress to a negative(tensile) stress and thus exhibits a stress value of zero.

According to the convention normally used in the art, compression orcompressive stress is expressed as a negative (<0) stress and tension ortensile stress is expressed as a positive (>0) stress. Throughout thisdescription, however, CS is expressed as a positive or absolutevalue—i.e., as recited herein, CS=|CS|. The compressive stress (CS) mayhave a maximum at the surface of the glass, and the CS may vary withdistance d from the surface according to a function. Referring again toFIG. 1, a first compressive layer 120 extends from first surface 110 toa depth d₁ and a second compressive layer 122 extends from secondsurface 112 to a depth dz. Together, these segments define a compressionor CS of glass ceramic 100.

The compressive stress of both compressive stress regions (120, 122 inFIG. 1) is balanced by stored tension in the central region (130) of theglass ceramic. The DOC values may be approximated based on theconcentration profile of the ions exchanged into the glass ceramicarticles during the ion exchange treatment, such as the depth below thesurface of the glass ceramic article where the measured concentrationbecomes substantially equal to the concentration in the glass ceramicarticle prior to the ion exchange treatment.

Compressive stress layers may be formed in the glass ceramic by exposingthe glass to an ion exchange solution. In embodiments, the ion exchangesolution may contain molten nitrate salt. In some embodiments, the ionexchange solution may be molten KNO₃, molten NaNO₃, molten LiNO₃, orcombinations thereof. In embodiments, the ion exchange solution maycomprise less than or equal to about 100% molten KNO₃, such as less thanor equal to about 95% molten KNO₃, less than or equal to about 90%molten KNO₃, less than or equal to about 85% molten KNO₃, less than orequal to about 80% molten KNO₃, less than or equal to about 75% moltenKNO₃, less than or equal to about 70% molten KNO₃, less than or equal toabout 65% molten KNO₃, less than or equal to about 60% molten KNO₃, orless. In certain embodiments, the ion exchange solution may comprisegreater than or equal to about 20% molten NaNO₃, such as greater than orequal to about 25% molten NaNO₃, greater than or equal to about 30%molten NaNO₃, greater than or equal to about 35% molten NaNO₃, greaterthan or equal to about 40% molten NaNO₃, or more. In embodiments, theion exchange solution may comprise about 80% molten KNO₃ and about 20%molten NaNO₃, about 75% molten KNO₃ and about 25% molten NaNO₃, about70% molten KNO₃ and about 30% molten NaNO₃, about 65% molten KNO₃ andabout 35% molten NaNO₃, or about 60% molten KNO₃ and about 40% moltenNaNO₃, and all ranges and sub-ranges between the foregoing values. Inembodiments, the ion exchange solution may a molten salt bath includinga mixture of KNO₃, NaNO₃, and LiNO₃. In embodiments, other sodium andpotassium salts may be used in the ion exchange solution, such as, forexample sodium or potassium nitrites, phosphates, or sulfates. Inembodiments, the ion exchange solution may contain silicic acid, such asless than or equal to about 1 wt % silicic acid.

The glass ceramic may be exposed to the ion exchange solution by dippingthe glass ceramic into a bath of the ion exchange solution, spraying theion exchange solution onto the glass ceramic, or otherwise physicallyapplying the ion exchange solution to the glass ceramic. Upon exposureto the glass ceramic, the ion exchange solution may, according toembodiments, be at a temperature from greater than or equal to 400° C.to less than or equal to 500° C., such as from greater than or equal to410° C. to less than or equal to 490° C., from greater than or equal to420° C. to less than or equal to 480° C., from greater than or equal to430° C. to less than or equal to 470° C., or from greater than or equalto 440° C. to less than or equal to 460° C., and all ranges andsub-ranges between the foregoing values. In embodiments, the glassceramic may be exposed to the ion exchange solution for a duration fromgreater than or equal to 4 hours to less than or equal to 48 hours, suchas from greater than or equal to 8 hours to less than or equal to 44hours, from greater than or equal to 12 hours to less than or equal to40 hours, from greater than or equal to 16 hours to less than or equalto 36 hours, from greater than or equal to 20 hours to less than orequal to 32 hours, or from greater than or equal to 24 hours to lessthan or equal to 28 hours, and all ranges and sub-ranges between theforegoing values.

The ion exchange process may be performed in an ion exchange solutionunder processing conditions that provide an improved compressive stressprofile as disclosed, for example, in U.S. Patent ApplicationPublication No. 2016/0102011, which is incorporated herein by referencein its entirety.

After an ion exchange process is performed, it should be understood thata composition at the surface of the glass ceramic may be different thanthe composition of the as-formed glass ceramic (i.e., the glass ceramicbefore it undergoes an ion exchange process). This results from one typeof alkali metal ion in the glass phase of the as-formed glass ceramic,such as, for example Li⁺ or Na⁺, being replaced with larger alkali metalions, such as, for example Na⁺ or K⁺, respectively. However, thecomposition of the glass ceramic at or near the center of the depth ofthe glass article will, in embodiments, be the least influenced by theion exchange treatment and may have a composition substantially the sameas or the same as the as-formed glass ceramic.

In embodiments, the ion exchanged glass ceramic articles may have asurface compressive stress of greater than or equal to about 250 MPa,such as greater than or equal to about 260 MPa, greater than or equal toabout 270 MPa, greater than or equal to about 280 MPa, greater than orequal to about 290 MPa, greater than or equal to about 300 MPa, greaterthan or equal to about 310 MPa, greater than or equal to about 320 MPa,greater than or equal to about 330 MPa, greater than or equal to about340 MPa, greater than or equal to about 350 MPa, greater than or equalto about 360 MPa, greater than or equal to about 370 MPa, greater thanor equal to about 380 MPa, greater than or equal to about 390 MPa,greater than or equal to about 400 MPa, greater than or equal to about410 MPa, greater than or equal to about 420 MPa, greater than or equalto about 430 MPa, greater than or equal to about 440 MPa, greater thanor equal to about 450 MPa, greater than or equal to about 460 MPa,greater than or equal to about 470 MPa, greater than or equal to about480 MPa, greater than or equal to about 490 MPa, greater than or equalto about 500 MPa, greater than or equal to about 510 MPa, greater thanor equal to about 520 MPa, greater than or equal to about 530 MPa,greater than or equal to about 540 MPa, greater than or equal to about550 MPa, greater than or equal to about 560 MPa, greater than or equalto about 570 MPa, greater than or equal to about 580 MPa, greater thanor equal to about 590 MPa, greater than or equal to about 600 MPa,greater than or equal to about 610 MPa, greater than or equal to about620 MPa, greater than or equal to about 630 MPa, or greater than orequal to about 640 MPa. In embodiments, the ion exchanged glass ceramicarticles may have a surface compressive stress from greater than orequal to about 250 MPa to less than or equal to about 650 MPa, such asgreater than or equal to about 260 MPa to less than or equal to about640 MPa, greater than or equal to about 270 MPa to less than or equal toabout 630 MPa, greater than or equal to about 280 MPa to less than orequal to about 620 MPa, greater than or equal to about 290 MPa to lessthan or equal to about 610 MPa, greater than or equal to about 300 MPato less than or equal to about 600 MPa, greater than or equal to about310 MPa to less than or equal to about 590 MPa, greater than or equal toabout 320 MPa to less than or equal to about 580 MPa, greater than orequal to about 330 MPa to less than or equal to about 570 MPa, greaterthan or equal to about 340 MPa to less than or equal to about 560 MPa,greater than or equal to about 350 MPa to less than or equal to about550 MPa, greater than or equal to about 360 MPa to less than or equal toabout 540 MPa, greater than or equal to about 370 MPa to less than orequal to about 530 MPa, greater than or equal to about 380 MPa to lessthan or equal to about 520 MPa, greater than or equal to about 390 MPato less than or equal to about 510 MPa, greater than or equal to about400 MPa to less than or equal to about 500 MPa, greater than or equal toabout 410 MPa to less than or equal to about 490 MPa, greater than orequal to about 420 MPa to less than or equal to about 480 MPa, greaterthan or equal to about 430 MPa to less than or equal to about 470 MPa,greater than or equal to about 440 MPa to less than or equal to about460 MPa, or about 450 MPa, and all ranges and sub-ranges between theforegoing values.

In embodiments, the ion exchanged glass ceramic articles may have adepth of the compressive stress layer (depth of compression) of greaterthan or equal to about 400 μm, such as greater than or equal to about410 μm, greater than or equal to about 420 μm, greater than or equal toabout 430 μm, greater than or equal to about 440 μm, greater than orequal to about 450 μm, greater than or equal to about 460 μm, greaterthan or equal to about 470 μm, greater than or equal to about 480 μm,greater than or equal to about 490 μm, greater than or equal to about500 μm, or more. In embodiments, the ion exchanged glass ceramicarticles may have a depth of compression of greater than or equal toabout 40 μm, such as greater than or equal to about 50 μm, greater thanor equal to about 60 μm, greater than or equal to about 70 μm, greaterthan or equal to about 80 μm, greater than or equal to about 90 μm,greater than or equal to about 100 μm, or more. In embodiments, thedepth of compression may be from greater than or equal to about 40 μm toless than or equal to 500 μm, such as from greater than or equal toabout 50 μm to less than or equal to about 480 μm, from greater than orequal to about 60 μm to less than or equal to about 460 μm, from greaterthan or equal to about 70 μm to less than or equal to about 440 μm, fromgreater than or equal to about 80 μm to less than or equal to about 420μm, from greater than or equal to about 90 μm to less than or equal toabout 400 μm, from greater than or equal to about 100 μm to less than orequal to about 380 μm, from greater than or equal to about 120 μm toless than or equal to about 360 μm, from greater than or equal to about140 μm to less than or equal to about 340 μm, from greater than or equalto about 160 μm to less than or equal to about 320 μm, from greater thanor equal to about 180 μm to less than or equal to about 300 μm, fromgreater than or equal to about 200 μm to less than or equal to about 280μm, from greater than or equal to about 220 μm to less than or equal toabout 260 μm, about 240 μm, and any and all sub-ranges formed from theseendpoints.

In embodiments, the ion exchanged glass ceramic articles may have adepth of the compressive stress layer (depth of compression) of greaterthan or equal to about 0.05t where t is the thickness of the glassceramic article, such as greater than or equal to about 0.1t, greaterthan or equal to about 0.15t, greater than or equal to about 0.2t, ormore. In embodiments, the glass ceramic articles may have a depth ofcompression from greater than or equal to about 0.05t to less than orequal to 0.25t where t is the thickness of the glass ceramic article,such as from greater than or equal to about 0.1t to less than or equalto 0.2t, or about 0.05t, and any and all sub-ranges formed from theseendpoints.

In embodiments, the ion exchanged glass ceramic may have a highstrength. In some embodiments, the ion exchanged glass ceramic has astrength of greater than or equal to about 900 MPa, such as greater thanor equal to about 910 MPa, greater than or equal to about 920 MPa,greater than or equal to about 930 MPa, greater than or equal to about940 MPa, greater than or equal to about 950 MPa, greater than or equalto about 960 MPa, greater than or equal to about 970 MPa, greater thanor equal to about 980 MPa, greater than or equal to about 990 MPa,greater than or equal to about 1000 MPa, or more. The strength refers tothe strength as measured by the ring-on-ring test described below. Inembodiments, the ion exchanged glass ceramic has a strength from greaterthan or equal to about 900 MPa to less than or equal to about 1000 MPa,such as greater than or equal to about 910 MPa to less than or equal toabout 990 MPa, greater than or equal to about 920 MPa to less than orequal to about 980 MPa, greater than or equal to about 930 MPa to lessthan or equal to about 970 MPa, greater than or equal to about 940 MPato less than or equal to about 960 MPa, or about 950 MPa, and any andall sub-ranges formed from these endpoints. In embodiments, the ionexchanged glass ceramic has a strength of greater than or equal to about700 MPa.

The glass ceramic articles may have any appropriate geometry. Inembodiments, the glass ceramic articles may have a thickness of greaterthan or equal to about 0.4 mm, such as greater than or equal to about0.5 mm, greater than or equal to about 0.6 mm, greater than or equal toabout 0.7 mm, greater than or equal to about 0.8 mm, greater than orequal to about 0.9 mm, greater than or equal to about 1.0 mm, greaterthan or equal to about 1.5 mm, greater than or equal to about 2.0 mm, ormore. In embodiments, the glass ceramic articles may have a thicknessfrom greater than or equal to about 0.4 mm to less than or equal toabout 2.0 mm, such as from greater than or equal to about 0.5 mm to lessthan or equal to about 1.5 mm, from greater than or equal to about 0.6mm to less than or equal to about 1.0 mm, from greater than or equal toabout 0.7 mm to less than or equal to about 0.9 mm, about 0.8 mm, andany and all sub-ranges formed from these endpoints. In embodiments, theglass ceramic articles have a thickness in the range from greater thanor equal to about 0.8 mm to less than or equal to about 1.0 mm.

The glass ceramic articles disclosed herein may be incorporated intoanother article such as an article with a display (or display articles)(e.g., consumer electronics, including mobile phones, tablets,computers, navigation systems, and the like), architectural articles,transportation articles (e.g., automobiles, trains, aircraft, sea craft,etc.), appliance articles, or any article that requires somescratch-resistance, abrasion resistance or a combination thereof. Anexemplary article incorporating any of the glass ceramic articlesdisclosed herein is shown in FIGS. 2A and 2B. Specifically, FIGS. 2A and2B show a consumer electronic device 200 including a housing 202 havingfront 204, back 206, and side surfaces 208; electrical components (notshown) that are at least partially inside or entirely within the housingand including at least a controller, a memory, and a display 210 at oradjacent to the front surface of the housing; and a cover substrate 212at or over the front surface of the housing such that it is over thedisplay. In some embodiments, at least a portion of the housing 202 mayinclude any of the glass ceramic articles disclosed herein.

EXAMPLES

Embodiments will be further clarified by the following examples. Itshould be understood that these examples are not limiting to theembodiments described above.

Glass ceramics having components, in wt %, listed in Table 1 below wereprepared and cerammed according to the indicated ceramming cycles. Theceramming cycles included a ramp rate of 5° C/minute from roomtemperature to the nucleation temperature. In Table 1, the individualsteps of the ceramming cycle are listed as a temperature and hold timein separate lines of the ceramming cycle entry, with three distinctceramming cycle steps in each of the examples.

TABLE 1 1 2 3 4 5 6 SiO₂ 69.2 68.8 68.5 69.0 69.4 70.7 Al₂O₃ 8.2 8.2 8.18.2 8.2 8.4 B₂O₃ 0.0 0.0 0.0 0.5 0.5 0.5 Li₂O 9.5 9.4 9.4 9.4 9.5 9.7Na₂O 0.9 1.5 1.9 1.5 0.9 0.9 ZrO₂ 3.5 3.5 3.5 3.5 3.5 1.8 P₂O₅ 2.3 2.32.3 2.3 2.3 2.3 TiO₂ 2.7 2.6 2.6 2.6 2.7 2.7 Fe₂O₃ 2.7 2.6 2.6 1.8 1.81.8 NiO 0.9 0.9 0.9 0.9 0.9 0.9 Co₃O₄ 0.2 0.2 0.2 0.2 0.2 0.2 MnO₂ 0.00.0 0.0 0.0 0.0 0.0 Ceramming 600° C./4 hr 600° C./4 hr 600° C./4 hr540° C./4 hr 540° C./4 hr 600° C./4 hr cycle 650° C./4 hr 650° C./4 hr650° C./4 hr 600° C./4 hr 600° C./4 hr 650° C. /4 hr 700° C./4 hr 700°C./4 hr 710° C./4 hr 700° C./2 hr 700° C./2 hr 700° C. /2 hr Phaseβ-quartz, Petalite, Petalite, Petalite, β-quartz, β-quartz, assemblagepetalite, β-quartz, lithium β-quartz, petalite, lithium cristobalite,lithium disilicate, cristobalite, cristobalite, disilicate, lithiumdisilicate, β-quartz lithium lithium β-spodumene metasilicatecristobalite, metasilicate metasilicate lithium metasilicate AppearanceBlack Black Black Black Black Black Color L* = 24.86  L* = 25.26  L* =27.23  coordinates a* = 0.17  a* = 0.03  a* = −0.07 b* = −0.05 b* =−0.69 b* = −1.15 K_(ic) 1.15 0.97 0.94 0.95 (MPa · m^(0.5)) RoR (MPa)291 RoR (MPa) 952 post IOX 24 hour 1085 1065 1025 1050 1065 1090Liquidus temp air (° C.) Liquidus 2980 4870 3280 3500 2371 viscosity(poise) Liquidus β-spodumene β-spodumene β-spodumene β-spodumeneβ-spodumene β-spodumene phase 7 8 9 10 11 12 SiO₂ 69.0 70.3 67.9 67.368.5 68.5 Al₂O₃ 8.9 9.1 8.1 8.0 8.7 9.6 B₂O₃ 0.2 0.2 0.0 0.0 0.0 0.0Li₂O 10.5 10.7 9.3 9.2 8.7 7.9 Na₂O 0.4 0.4 1.9 1.9 1.9 1.9 ZrO₂ 1.8 1.83.5 3.4 3.5 3.5 P₂O₅ 1.9 2.0 2.3 2.2 2.3 2.3 TiO₂ 2.6 2.7 3.0 3.4 2.62.6 Fe₂O₃ 2.6 1.8 3.0 3.4 2.6 2.6 NiO 0.9 0.9 0.9 0.9 0.9 0.9 Co₃O₄ 0.20.2 0.2 0.2 0.2 0.2 MnO₂ 0.9 0.0 0.0 0.0 0.0 0.0 Ceramming 600° C./4 hr600° C./4 hr 600° C./4 hr 600° C./4 hr 600° C./4 hr 600° C./4 hr cycle650° C./4 hr 650° C./4 hr 650° C./4 hr 650° C./4 hr 650° C./4 hr 650°C./4 hr 700° C./2 hr 700° C./2 hr 710° C./4 hr 710° C./4 hr 710° C./4 hr710° C./4 hr Phase β-quartz, β-quartz, petalite, β-quartz, β-quartz,β-quartz, assemblage lithium lithium lithium petalite, petalite, lithiumdisilicate, disilicate, disilicate, lithium lithium metasilicate,petalite, petalite, β-quartz, metasilicate, metasilicate, β- lithiumlithium β-spodumene cristobalite lithium spodumene, metasilicatemetasilicate disilicate, cristobalite β-spodumene Appearance Black BlackBlack Black Black Black Color L* = 26.93  L* = 26.90  L* = 27.11  L* =28.49  coordinates a* = −0.08 a* = −0.04 a* = −0.04 a* = −0.24 b* =−1.55 b* = −1.48 b* = −0.92 b* = −1.54 K_(ic) 1.06 (MPa · m^(0.5)) RoR(MPa) RoR (MPa) post IOX 24 hour 1090 1045 1060 1070 1175 Liquidus tempair (° C.) Liquidus 1057 3444 2345 3721 1750 viscosity (poise) Liquidusβ-spodumene β-spodumene β-spodumene β-spodumene Zircon phase

The phase assemblage of the glass ceramics was determined using X-raydiffraction (XRD) analysis of the cerammed samples. The appearance ofthe glass ceramics is an impression based on observation of the samples.The color coordinates were measured using an X-rite Ci7 F02 illuminantunder SCI UVC conditions. The liquidus temperature was measured inaccordance with ASTM C829-81 (2015), titled “Standard Practice forMeasurement of Liquidus Temperature of Glass by the Gradient FurnaceMethod” for the precursor glass. The viscosity of the glass at theliquidus temperature is measured in accordance with ASTM C965-96(2012),titled “Standard Practice for Measuring Viscosity of Glass Above theSoftening Point” to determine the liquidus viscosity. The fracturetoughness value (Kic) was measured by the chevron notched short bar(CNSB) method disclosed in Reddy, K. P. R. et al, “Fracture ToughnessMeasurement of Glass and Ceramic Materials Using Chevron-NotchedSpecimens,” J. Am. Ceram. Soc., 71 [6], C-310-C-313 (1988) except thatY*_(m) is calculated using equation 5 of Bubsey, R. T. et al.,“Closed-Form Expressions for Crack-Mouth Displacement and StressIntensity Factors for Chevron-Notched Short Bar and Short Rod SpecimensBased on Experimental Compliance Measurements,” NASA TechnicalMemorandum 83796, pp. 1-30 (October 1992). The Ring-on-Ring (RoR)strength was measured as described in further detail below.

Comparative Examples 1 and 2 were produced with the compositions andceramming cycles described in Table 2 below.

TABLE 2 Comp. Comp. Ex. 1 Ex. 2 SiO₂ 64.1 57.2 Al₂O₃ 21.2 21.1 B₂O₃ 0.05.3 Li₂O 3.6 0.0 Na₂O 0.4 12.7 MgO 1.7 1.1 ZnO 1.3 0.0 TiO₂ 4.8 1.2 SnO₂0.4 0.1 Fe₂O₃ 2.6 1.3 Co₃O₄ 0.0 0.0 Ceramming  780° C./2 hr 630° C./2 hrcycle 1000° C./4 hr 700° C./4 hr

The transmittance of Examples 3 of Table 1 and Comparative Examples 1and 2 of Table 2 was measured for 0.8 mm thick samples, as describedabove. As shown in FIG. 3, the glass ceramic of Example 3 has atransmittance of less than 1% in the visible wavelength range.

A sample of Example 3 with a thickness of 1.0 mm was ion exchanged in a60 wt % KNO₃ and 40 wt % NaNO₃ bath at a temperature of 470° C. for atime period of 4 hours. The ring-on-ring strength of the sample wasmeasured before and after the ion exchange treatment, as describedbelow. The Weibull plot of the results of the ring-on-ring test is shownin FIG. 4.

The Ring-on-Ring (RoR) test is a surface strength measurement fortesting flat glass specimens, and ASTM C1499-09(2013), entitled“Standard Test Method for Monotonic Equibiaxial Flexural Strength ofAdvanced Ceramics at Ambient Temperature,” serves as the basis for theRoR test methodology described herein. The contents of ASTM C1499-09 areincorporated herein by reference in their entirety. The specimen was notabraded prior to ring-on-ring testing.

For the RoR test, a sample as shown in FIG. 6 is placed between twoconcentric rings of differing size to determine equibiaxial flexuralstrength (i.e., the maximum stress that a material is capable ofsustaining when subjected to flexure between two concentric rings). Inthe RoR configuration 400, the glass ceramic article 410 is supported bya support ring 420 having a diameter D2. A force F is applied by a loadcell (not shown) to the surface of the glass ceramic article by aloading ring 430 having a diameter D1.

The ratio of diameters of the loading ring and support ring D1/D2 may bein a range from 0.2 to 0.5. In some embodiments, D1/D2 is 0.5. Loadingand support rings 130, 120 should be aligned concentrically to within0.5% of support ring diameter D2. The load cell used for testing shouldbe accurate to within ±1% at any load within a selected range. Testingis carried out at a temperature of 23±2° C. and a relative humidity of40±10%.

For fixture design, the radius r of the protruding surface of theloading ring 430 is in a range of h/2≤r≤3h/2, where h is the thicknessof glass-based article 410. Loading and support rings 430, 420 are madeof hardened steel with hardness HRc>40. RoR fixtures are commerciallyavailable.

The intended failure mechanism for the RoR test is to observe fractureof the glass ceramic article 410 originating from the surface 430 awithin the loading ring 430. Failures that occur outside of thisregion—i.e., between the loading ring 430 and support ring 420—areomitted from data analysis. Due to the thinness and high strength of theglass ceramic article 410, however, large deflections that exceed ½ ofthe specimen thickness h are sometimes observed. It is therefore notuncommon to observe a high percentage of failures originating fromunderneath the loading ring 430. Stress cannot be accurately calculatedwithout knowledge of stress development both inside and under the ring(collected via strain gauge analysis) and the origin of failure in eachspecimen. RoR testing therefore focuses on peak load at failure as themeasured response.

The strength of glass-based article depends on the presence of surfaceflaws. However, the likelihood of a flaw of a given size being presentcannot be precisely predicted, as the strength of glass is statisticalin nature. A probability distribution can therefore be used as astatistical representation of the data obtained.

A sample of Example 3 was ion exchange in a NaNO₃ bath at 430° C. for 16hours. The concentration of Na₂O in the ion exchanged sample as afunction of depth below the surface was then measured using an electronmicroprobe, and the resulting Na₂O concentration profile (in mol %) isshown in FIG. 5.

All compositional components, relationships, and ratios described inthis specification are provided in wt % unless otherwise stated. Allranges disclosed in this specification include any and all ranges andsubranges encompassed by the broadly disclosed ranges whether or notexplicitly stated before or after a range is disclosed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the embodiments describedherein without departing from the spirit and scope of the claimedsubject matter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A glass ceramic, comprising: at least one lithiumsilicate crystal phase as a primary crystal phase; and at least one ofpetalite, β-quartz, β-spodumene, cristobalite, and lithium phosphate asa secondary crystal phase, wherein the glass ceramic is characterized bythe following color coordinates: L*: 20.0 to 40.0; a*: −1.0 to 1.0; andb*: −5.0 to 2.0.
 2. The glass ceramic of claim 1, wherein the primarycrystal phase is a lithium metasilicate.
 3. The glass ceramic of claim1, wherein the primary crystal phase is lithium disilicate.
 4. The glassceramic of claim 1, wherein the glass ceramic has a transmittance ofless than 1% in the visible light range.
 5. The glass ceramic of claim1, wherein the glass ceramic has a ring-on-ring strength of at least 290MPa.
 6. The glass ceramic of claim 1, wherein the glass ceramic has afracture toughness of greater than or equal to 0.9 MPa·m^(0.5) to lessthan or equal to 2.0 MPa·m^(0.5).
 7. The glass ceramic of claim 1,wherein the glass ceramic has a fracture toughness of greater than orequal to 1.0 MPa·m^(0.5) to less than or equal to 1.5 MPa·m^(0.5). 8.The glass ceramic of claim 1, further comprising: 55.0 wt % to 75.0 wt %SiO₂; 2.0 wt % to 20.0 wt % Al₂O₃; 0 wt % to 5.0 wt % B₂O₃; 5.0 wt % to15.0 wt % Li₂O; 0 wt % to 5.0 wt % Na₂O; 0 wt % to 4.0 wt % K₂O; 0 wt %to 8.0 wt % MgO; 0 wt % to 10.0 wt % ZnO; 0.5 wt % to 5.0 wt % TiO₂; 1.0wt % to 6.0 wt % P₂O_(5;) 2.0 wt % to 10.0 wt % ZrO₂; 0 wt % to 0.4 wt %CeO₂; 0.05 wt % to 0.5 wt % SnO+SnO₂; 0.1 wt % to 5.0 wt % FeO+Fe₂O₃;0.1 wt % to 5.0 wt % NiO; 0.1 wt % to 5.0 wt % Co₃O₄; 0 wt % to 4.0 wt %MnO+MnO₂+Mn₂O₃; 0 wt % to 2.0 wt % Cr₂O₃; 0 wt % to 2.0 wt % CuO; and 0wt % to 2.0 wt % V₂O₅.
 9. The glass ceramic of claim 1, furthercomprising: 65.0 wt % to 75.0 wt % SiO₂; 7.0 wt % to 11.0 wt % Al₂O₃;6.0 wt % to 11.0 wt % Li₂O; 2.0 wt % to 4.0 wt % TiO₂; 1.5 wt % to 2.5wt % P₂O₅; 2.0 wt % to 4.0 wt % ZrO₂; 1.0 wt % to 4.0 wt % FeO+Fe₂O₃;0.5 wt % to 1.5 wt % NiO; and 0.1 wt % to 0.4 wt % Co₃O₄.
 10. The glassceramic of claim 1, wherein the glass ceramic has a crystallinity ofgreater than 50 wt %.
 11. The glass ceramic of claim 1, wherein theglass ceramic is ion exchanged and comprises a compressive stress layerextending from a surface of the glass ceramic to a depth of compression.12. The glass ceramic of claim 11, wherein the glass ceramic has acompressive stress at the surface of at least 250 MPa.
 13. The glassceramic of claim 11, wherein the glass ceramic has a compressive stressat the surface of greater than or equal to 250 MPa to less than or equalto 650 MPa.
 14. The glass ceramic of claim 11, wherein the depth ofcompression is at least 0.05t, where t is a thickness of glass ceramic.15. The glass ceramic of claim 11, wherein the glass ceramic has aring-on-ring strength of at least 900 MPa.
 16. A consumer electronicproduct, comprising: a housing comprising a front surface, a backsurface and side surfaces; electrical components at least partiallywithin the housing, the electrical components comprising at least acontroller, a memory, and a display, the display at or adjacent thefront surface of the housing; and a cover glass disposed over thedisplay, wherein at least a portion of the housing comprises the glassceramic of claim
 1. 17. A consumer electronic product, comprising: ahousing comprising a front surface, a back surface and side surfaces;electrical components at least partially within the housing, theelectrical components comprising at least a controller, a memory, and adisplay, the display at or adjacent the front surface of the housing;and a cover glass disposed over the display, wherein at least a portionof the housing comprises the glass ceramic of claim
 11. 18. A method,comprising: ceramming a precursor glass-based article to form a glassceramic, wherein the glass ceramic comprises: at least one lithiumsilicate crystal phase as a primary crystal phase; and at least one ofpetalite, β-quartz, β-spodumene, cristobalite, and lithium phosphate asa minor crystal phase, and the glass ceramic is characterized by thefollowing color coordinates: L*: 20.0 to 40.0; a*: −1.0 to 1.0; and b*:−5.0 to 2.0.
 19. The method of claim 18, wherein the ceramming occurs ata temperature of greater than or equal to 500° C. to less than or equalto 900° C.
 20. The method of claim 18, wherein the ceramming occurs fora period of greater than or equal to 6 hours to less than or equal to 16hours.
 21. The method of claim 18, further comprising ion exchanging theglass ceramic.
 22. The method of claim 18, wherein the precursorglass-based article comprises: 55.0 wt % to 75.0 wt % SiO₂; 2.0 wt % to20.0 wt % Al₂O₃; 0 wt % to 5.0 wt % B₂O₃; 5.0 wt % to 15.0 wt % Li₂O; 0wt % to 5.0 wt % Na₂O; 0 wt % to 4.0 wt % K₂O; 0 wt % to 8.0 wt % MgO; 0wt % to 10.0 wt % ZnO; 0.5 wt % to 5.0 wt % TiO₂; 1.0 wt % to 6.0 wt %P₂O₅; 2.0 wt % to 10.0 wt % ZrO₂; 0 wt % to 0.4 wt % CeO₂; 0.05 wt % to0.5 wt % SnO+SnO₂; 0.1 wt % to 5.0 wt % FeO+Fe₂O₃; 0.1 wt % to 5.0 wt %NiO; 0.1 wt % to 5.0 wt % Co₃O₄; 0 wt % to 4.0 wt % MnO+MnO₂+Mn₂O₃; 0 wt% to 2.0 wt % Cr₂O₃; 0 wt % to 2.0 wt % CuO; and 0 wt % to 2.0 wt %V₂O₅.
 23. The method of claim 18, wherein the precursor glass-basedarticle comprises: 65.0 wt % to 75.0 wt % SiO₂; 7.0 wt % to 11.0 wt %Al₂O₃; 6.0 wt % to 11.0 wt % Li₂O; 2.0 wt % to 4.0 wt % TiO₂; 1.5 wt %to 2.5 wt % P₂O₅; 2.0 wt % to 4.0 wt % ZrO₂; 1.0 wt % to 4.0 wt %FeO+Fe₂O₃; 0.5 wt % to 1.5 wt % NiO; and 0.1 wt % to 0.4 wt % Co₃O₄. 24.A glass, comprising: 55.0 wt % to 75.0 wt % SiO₂; 2.0 wt % to 20.0 wt %Al₂O₃; 0 wt % to 5.0 wt % B₂O₃; 5.0 wt % to 15.0 wt % Li₂O; 0 wt % to5.0 wt % Na₂O; 0 wt % to 4.0 wt % K₂O; 0 wt % to 8.0 wt % MgO; 0 wt % to10.0 wt % ZnO; 0.5 wt % to 5.0 wt % TiO₂; 1.0 wt % to 6.0 wt % P₂O₅; 2.0wt % to 10.0 wt % ZrO₂; 0 wt % to 0.4 wt % CeO₂; 0.05 wt % to 0.5 wt %SnO+SnO₂; 0.1 wt % to 5.0 wt % FeO+Fe₂O₃; 0.1 wt % to 5.0 wt % NiO; 0.1wt % to 5.0 wt % Co₃O₄; 0 wt % to 4.0 wt % MnO+MnO₂+Mn₂O₃; 0 wt % to 2.0wt % Cr₂O₃; 0 wt % to 2.0 wt % CuO; and 0 wt % to 2.0 wt % V₂O₅.
 25. Theglass of claim 24, comprising: 65.0 wt % to 75.0 wt % SiO₂; 7.0 wt % to11.0 wt % Al₂O₃; 6.0 wt % to 11.0 wt % Li₂O; 2.0 wt % to 4.0 wt % TiO₂;1.5 wt % to 2.5 wt % P₂O₅; 2.0 wt % to 4.0 wt % ZrO₂; 1.0 wt % to 4.0 wt% FeO+Fe₂O₃; 0.5 wt % to 1.5 wt % NiO; and 0.1 wt % to 0.4 wt % Co₃O₄.